A latch device on a vehicle tailgate having upper and lower doors comprises an open handle assembly for releasing a lower latch assembly from a lower striker, a key cylinder for releasing an upper latch assembly and an upper striker, a coupling mechanism displaceable between a locked position for disabling an opening operation of the handle assembly and an unlocked position for enabling the opening operation of the handle assembly. The upper latch assembly has a latch and a ratchet. The ratchet is displaceable between an engaging position for engaging with the latch located in a door-closed position and an initial position for making contact with the latch located in a door-open position. The coupling mechanism is displaced to the locked position when the ratchet is in the engaging position and displaced to the unlocked position when the ratchet is in the initial position.